Recoat assemblies for additive manufacturing systems and methods for using the same

Abstract

A method for forming an object includes moving a recoat assembly ( 200 ) in a coating direction over a build material, wherein the recoat assembly ( 200 ) comprises a first roller ( 202 ) and a second roller ( 204 ) that is spaced apart from the first roller; rotating the first roller ( 202 ) of the recoat assembly in a counter-rotation direction, such that a bottom of the first roller moves in the coating direction; contacting the build material with the first roller of the recoat assembly, thereby fluidizing at least a portion of the build material; irradiating, with a front energy source ( 260 ) coupled to a front end of the recoat assembly, an initial layer of build material positioned in a build area; subsequent to irradiating the initial layer of build material, spreading the build material on the build area with the first roller, thereby depositing a second layer of the build material over the initial layer of build material; and subsequent to spreading the second layer of the build material, irradiating, with a rear energy source ( 262 ) positioned rearward of the front energy source, the second layer of build material within the build area.

The invention claimed is: 
     
       1. A method for forming an object, the method comprising:
 moving a recoat assembly in a coating direction over a build material, wherein the recoat assembly comprises a first roller and a second roller that is spaced apart from the first roller; 
 rotating the first roller of the recoat assembly in a counter-rotation direction, such that a bottom of the first roller moves in the coating direction; 
 contacting the build material with the first roller of the recoat assembly, thereby fluidizing at least a portion of the build material; 
 irradiating, with a front energy source coupled to a front end of the recoat assembly, an initial layer of build material positioned in a build area; 
 subsequent to irradiating the initial layer of build material, spreading the build material on the build area with the first roller, thereby depositing a second layer of the build material over the initial layer of build material; and 
 subsequent to spreading the second layer of the build material, irradiating, with a rear energy source positioned rearward of the front energy source, the second layer of build material within the build area. 
 
     
     
       2. The method of  claim 1 , wherein the second roller is positioned above the first roller in a vertical direction, such that the second roller does not contact the build material. 
     
     
       3. The method of  claim 1 , wherein the first roller is a front roller and the second roller is a rear roller positioned rearward of the first roller. 
     
     
       4. The method of  claim 3 , further comprising:
 rotating the rear roller in a rotation direction that is the opposite of the counter-rotation direction; and 
 contacting the second layer of the build material within the build area with the rear roller. 
 
     
     
       5. The method of  claim 4 , wherein rotating the rear roller in the rotation direction comprises rotating the rear roller at a rotational velocity that corresponds to a linear velocity of the recoat assembly. 
     
     
       6. The method of  claim 1 , further comprising, subsequent to at least one of irradiating the initial layer of build material with the front energy source and irradiating the second layer of build material with the rear energy source, detecting a temperature of the irradiated build material with a temperature sensor. 
     
     
       7. The method of  claim 6 , further comprising changing at least one parameter of the front energy source or the rear energy source based at least in part on the detected temperature. 
     
     
       8. The method of  claim 6 , wherein at least one of irradiating the initial layer of build material with the front energy source and irradiating the second layer of build material with the rear energy source comprises applying a predetermined power to the front energy source or the rear energy source, the method further comprising changing the predetermined power based at least in part on the detected temperature. 
     
     
       9. A method for forming an object, the method comprising:
 moving a recoat assembly over a build material, wherein the recoat assembly comprises a first roller and a second roller that is spaced apart from the first roller; 
 moving the second roller above the first roller in a vertical direction; 
 rotating the first roller of the recoat assembly in a counter-rotation direction, such that a bottom of the first roller moves in a coating direction; 
 contacting the build material with the first roller of the recoat assembly, thereby fluidizing at least a portion of the build material, while the second roller is spaced apart from the build material in the vertical direction; and 
 moving the fluidized build material with the first roller, thereby depositing a second layer of the build material over an initial layer of build material positioned in a build area. 
 
     
     
       10. The method of  claim 9 , further comprising, subsequent to depositing the second layer of build material, moving the first roller upward in the vertical direction such that the first roller is spaced apart from the second layer of build material and moving the recoat assembly to a home position in a direction that is the opposite of the coating direction. 
     
     
       11. The method of  claim 10 , wherein moving the recoat assembly to the home position comprises moving the recoat assembly at a return speed, and wherein moving the fluidized build material comprises moving the recoat assembly in the coating direction at a coating speed, wherein the return speed is greater than the coating speed. 
     
     
       12. The method of  claim 10 , further comprising, prior to moving the recoat assembly to the home position, lowering the second roller such that the second roller contacts the second layer of build material. 
     
     
       13. The method of  claim 12 , further comprising rotating the second roller in the counter-rotation direction. 
     
     
       14. The method of  claim 13 , wherein rotating the second roller in the counter-rotation direction comprises rotating the second roller at a rotational velocity that corresponds to a linear velocity of the recoat assembly moving to the home position. 
     
     
       15. The method of  claim 12 , wherein the second roller comprises a second roller diameter and the first roller comprises a first roller diameter, wherein the second roller diameter is greater than the first roller diameter. 
     
     
       16. A recoat assembly for an additive manufacturing system, the recoat assembly comprising:
 a base member; 
 a front roller rotatably coupled to the base member; 
 a rear roller rotatably coupled to the base member, wherein the front roller is spaced apart from the rear roller; 
 a front energy source coupled to the base member and positioned forward of the front roller, wherein the front energy source emits energy forward of the front roller; and 
 a rear energy source coupled to the base member and positioned rearward of the front energy source, wherein the rear energy source emits energy rearward of the front energy source subsequent to the front energy source emitting energy forward of the front roller. 
 
     
     
       17. The recoat assembly of  claim 16 , further comprising a vertical actuator coupled to at least one of the front roller and the rear roller, and the base member, wherein the vertical actuator moves the at least one of the front roller and the rear roller in a vertical direction with respect to the base member. 
     
     
       18. The recoat assembly of  claim 16 , further comprising a hard stop that restricts movement of the at least one of the front roller and the rear roller in a vertical direction. 
     
     
       19. The recoat assembly of  claim 16 , further comprising a vertical actuator coupled to the front roller and the rear roller such that the front roller and the rear roller are moveable with respect to the base member independently of one another. 
     
     
       20. The recoat assembly of  claim 19 , wherein the vertical actuator is a first vertical actuator coupled to the front roller, and the recoat assembly further comprises a second vertical actuator coupled to the rear roller, wherein the second vertical actuator moves the rear roller in a vertical direction with respect to the base member.